Protective Window Contamination Detection via Return Light Analysis

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Solution Overview

Problem

Laser processing devices face significant quality deterioration due to contamination of the protective window, which is not accurately detected in a timely manner, leading to delayed maintenance and processing defects.

Innovation Solution

A laser processing device equipped with a beam splitter, return light measurement unit, and pattern recognition using a discriminant function to detect contamination of the protective window by analyzing the intensity distribution of return light, issuing warnings and adjusting the window position to prevent excessive contamination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional contamination detection methods (temperature sensors, scattered light sensors) are used, then contamination can be detected, but the detection accuracy is insufficient leading to delayed maintenance timing

Engineering Contradiction:

Improvecontamination detection accuracyVSAvoidmaintenance timing delay

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The system continuously monitors return light intensity distribution during laser processing and provides real-time feedback about protective window contamination status. The measurement unit captures light reflected from the workpiece through the optical system, and the control unit compares this against reference values to detect contamination, enabling timely maintenance before processing quality deteriorates.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces conventional mechanical or simple optical detection methods (temperature sensors, scattered light sensors) with an optical measurement system that analyzes the intensity distribution of return light. This substitution enables more precise contamination detection by measuring how contamination affects light reflection patterns rather than relying on temperature changes or scattered light intensity alone.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If the protective window is monitored continuously to detect contamination early, then maintenance timing can be optimized, but the device complexity increases

Engineering Contradiction:

Improvelaser processing quality consistencyVSAvoiddetection system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The return light measurement unit serves multiple functions: it monitors protective window contamination, verifies optical system alignment, and provides feedback for process control. By using the same optical path and measurement mechanism for multiple purposes, the system achieves reliable contamination detection without adding separate dedicated detection systems, thereby limiting the increase in device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system uses the return light that naturally reflects from the workpiece during normal laser processing operations. This existing light path is repurposed for contamination detection without requiring additional light sources or separate measurement channels. The optical system essentially monitors itself by analyzing how contamination affects the return light characteristics during regular operation.

Inventive Principle:

Principle #25Self-service

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

Accurate detection and warning of protective window contamination enable timely maintenance, reducing processing defects and extending the maintenance period, ensuring consistent laser processing quality.

Implementation Method 1

a beam splitter disposed between the focusing lens and the protective window

Methodology Applied

Scientific EffectLight reflection and transmission: Reflection

Implementation Method 2

a focusing lens configured to focus a light output from the laser oscillator

Methodology Applied

Scientific EffectLight focusing: Focusing

Implementation Method 3

a return light measurement unit configured to measure intensity distribution of a return light reflected from a workpiece

Methodology Applied

Scientific EffectLight intensity measurement: Photoelectric Effect

Data Source

PatentUS10761037B2Laser processing device for determining the presence of contamination on a protective window

Publication Date: 2020.09.01 FANUC LTD

AI summary

A laser processing device includes a beam splitter disposed between a focusing lens and a protective window, a return light measurement unit configured to measure intensity distribution of a return light reflected from a workpiece and returning to an external optical system via the beam splitter, a storage unit configured to store at least one of normal pattern data representing the intensity distribution of the return light when the protective window is in normal condition and abnormal pattern data representing the intensity distribution of the return light when the protective window is contaminated, a processing unit configured to perform a process of detecting contamination of the protective window during laser processing based on measurement data about the return light and at least one of the normal pattern data and the abnormal pattern data, and a warning unit configured to warn of contamination of the protective window in accordance with the process.